This was our second visit to Penbay this year, last time our fastest lap was 2.17 and we were hoping to improve on that this time around. After running our current brake setup through the bias calculator we found that we had too much talk going to the rear discs, which would explain why the back end was a little happy when braking into corners. The easiest way to fix that and balance out the bias to the OEM spec (front 69% rear 31%) would be to change the rear pads to a lower friction, so what's exactly what we did.

Ideally we would have 0.43u pads on the rear to go with our front 0.50u race pads. We couldn't find any that were exactly 0.43u so we settled for our 0.45u street pads instead, which are close enough. Plus once they heat up to race temperature they will lose a little bit of friction anyway, so that's probably about right.

In addition to the new rear pads, we went full-out on the wheel camber, 3 degrees front and 2 degrees rear negative camber! Not very good for tyre wear, but that should have allowed us a lot more grip on the bends. We still have lots of room for more adjustment as we haven't touched the camber plates yet, we achieved 3 and 2 degrees by way of camber adjustment bolts on the lower mounts. Either way the Impreza is still an everyday road car, so I can't really run any more camber as I would be changing the tyres every 5,000km!

Penbay is a very level track, and as it's only 2 years old the road surface is still very smooth, so we had no issues with turning up the damping to 30 clicks (the hardest setting). Harder spring rates would have been better, but like I say we have to make the 200km trip back home after the track day so I'm glad we stuck to 8kg front 6kg rear. On top of that, we're still rallying in Taiwan so anything harder than what we are running at the moment wouldn't work. We do have lots of options available for the Impreza GD, and every spring rate we offer for any application includes matched damper valving. Here is what's available for the GD...

Front spring rates

8, 10, 12, 13kg

Rear spring rates

5, 6, 7, 8, 10kg

After 130km on the track, we were so low on fuel that the engine started to cut-out on the tighter bends due to the g-force. That's when you know it's time to call it a day. For some strange reason unknown to myself, there is no re-fueling station at the race track, so we would have had to make a 10km round trip to fill up. We only had half an hour of track time left, so it wasn't worth it.

We got the times back, and I was initially disappointed to find that our fastest lap was 2.13, only 4 seconds faster than our last trip. However when you consider the air temperature was 38 degrees, a full 10 degrees hotter than last time, we didn't do too badly. I imagine that if it was as cool as our last trip we could have taken 2-3 seconds off that time. This was the first time I have ever seen the oil temp gauge go over 40%, so there's no doubt the engine was struggling to deal with the extreme heat and humidity.

On the positive side, the PB brakes and coilovers performed perfectly. We didn't experience any brake fade over the 40 or so laps we completed, and we weren't taking it easy on them. We were braking late and hard into every corner, and exploring the limits of what they could take. Even after a 10 lap stint at full race speed we still had enough stopping power to initiate the ABS. The only factor limiting our stopping distance was the tyres. If you have larger and more sticky tyres, you can brake harder and slow down more quickly before the ABS kicks in.

So that pretty much sums it up, we will go back there in Autumn or Winter when it's a little cooler and see if we can't break 2.10!